1. Field of the Invention
This invention relates generally to vehicle body mounted power operated antennas and, more particularly, to a new and improved seal for preventing moisture intrusion into the vehicle body at full antenna mast extension.
2. Description of the Prior Art
In a typical power operated antenna installation on a vehicle body, a stationary tube is supported under a panel of the body in alignment with an aperture in the panel. A plurality of telescopically related tubes which form the antenna mast are housed in the stationary tube and are projected to extended positions by an electric motor driven linear actuator. When the mast is fully extended the lowest of the telescopic tubes projects out of the open end of the stationary tube and through an insulator disposed around the panel aperture between the lowest tube and the body panel. The necessary clearance between the insulator and the movable tube represents a potential source of moisture intrusion into the vehicle body below the apertured panel. In one known antenna installation, a rubber or similarly elastic grommet is supported on the insulator with a flange surrounding and sealing against the lowest movable mast section. The grommet flange enters a groove in the mast section to effect the seal. In another known proposal, the clearances between relatively movable mast sections are sealed by rubber or similarly elastic packings attached to one of the sections and slidably engaging the other. In still another proposal, the lowest movable tube section carries a sleeve which supports a rubber or similarly elastic O-ring having an outside diameter smaller than the inside diameter of the stationary tube so as not to interfere with relative sliding movement between the tubes. When the lowest movable tube approaches full extension, the O-ring is compressed against an inturned flange at the end of the stationary tube and a seal is formed around the movable tube. Each of these proposals requires a relatively elastic seal of rubber or like material which is subject to deterioration with age. A moisture seal arrangement according to this invention represents an improvement over these and other known proposals in that acceptable sealing is achieved in a simple and economical structure which does not require an elastic rubber-like material and is, therefore, less susceptible to deterioration with age.